Machine for printing images on articles

ABSTRACT

The machine ( 1 ) comprises a support structure ( 4, 11 ) in which there are: a thermal-transfer device ( 14 ) having a movable active surface ( 36   a;    136   a ) facing the path of the articles; supply and guide means ( 5 - 10 ) suitable for advancing a flexible ribbon (N) in steps along a predetermined route which extends partly between the active surface ( 36   a;    136   a ) of the thermal-transfer device ( 14 ) and the path of the articles, the flexible ribbon (N) carrying, at predetermined intervals, images formed with a thermally transferable ink; and drive devices ( 22 ) suitable for bringing about a vertical movement of the thermal-transfer device ( 14 ) towards the ribbon (N) and an article so as to press and heat the ribbon (N) against an article in order to bring about the transfer of an image carried by the ribbon (N). The supply and guide means comprise: three pairs of aligned and parallel guide rollers (R 1 ) disposed on the route of the ribbon (N) on upstream and downstream sides of the thermal-transfer device ( 14 ). The arrangement of the pairs of rollers (R 1 , R 2 , R 3 ) is such that the portions of the ribbon (N) which are included between the first and second pairs of rollers (R 1 , R 2 ) and the portions which are included between the second and third pairs of rollers (R 2 , R 3 ) are substantially parallel with one another. Movement devices ( 70; 170 ), associated with the first and with the second pairs of guide rollers (R 1 , R 2 ), are such that a movement of the second pair of rollers (R 2 ) is substantially equal to half of the corresponding movement of the first pair of rollers (R 1 ).

A machine for printing images on articles The present invention relatesin general to machines for printing images on articles such ascontainers or packages of products.

In the description and in the appended claims, the term “image”: isintended in a broad sense to mean text, a design or logo, a bar code, orany other two-dimensional graphical representation.

It is known to print codes and/or images of other types directly ontoalready-packaged products by the thermal transfer of ink from an inkedribbon.

The subject of the present invention is, in particular, a type ofmachine for printing images comprising a support structure in whichthere are:

-   -   a thermal-transfer device having a movable active surface in a        position operatively facing the path of the articles that are to        receive the printing,    -   supply and guide means suitable for advancing a flexible ribbon        in steps along a predetermined route which extends partly        between the active surface of the thermal-transfer device and        the path of the articles, the flexible ribbon carrying, at        predetermined intervals, on the face which is intended to face        the articles, images formed with a thermally transferable ink,        and    -   drive means suitable for bringing about a movement of the active        surface of the thermal-transfer device towards the ribbon and an        article so as to press and heat the ribbon against the article        in order to bring about the transfer of an image carried by the        ribbon onto the article.

Typically, the movement of the thermal-transfer device towards theribbon which carries the images and towards the article takes placevertically downwards from above.

If, during the vertical movement of the thermal-transfer device and ofthe portion of the ribbon which carries the image, even a slightslippage of the ribbon with the image takes place in a horizontaldirection, a poor and sometimes unacceptable printing result isobtained.

An object of the present invention is to provide a printing machine ofthe type defined above which prevents this problem.

This object is achieved, according to the invention, by a printingmachine the main characteristics of which are defined in appended claim1.

Further objects, characteristics and advantages of the invention willbecome clear from the following detailed description which is givenpurely by way of non-limiting example with reference to the appendeddrawings, in which:

FIG. 1 is a front view of a first printing machine according to thepresent invention,

FIGS. 2, 3 and 4 are partial sections taken substantially on the linesII-II, III-III and IV-IV of FIG. 1,

FIG. 5 is a front view of another printing machine according to thepresent invention,

FIG. 6 is a partial view from above, taken on the arrow VI of FIG. 5,

FIG. 7 is a partial section taken substantially on the line VII-VII ofFIG. 5,

FIG. 8 is a partial section taken substantially on the line VIII-VIII ofFIG. 7,

FIG. 9 is a partial view similar to that of FIG. 8 which shows some ofthe devices of the machine in a different operative condition,

FIG. 10 is a partial section taken substantially on the line X-X of FIG.5, and

FIGS. 11 and 12 are partial views similar to that shown in FIG. 10 andshow different operating conditions of the machine.

In the drawings, a thermal ink-transfer printing machine according tothe invention is generally indicated 1.

With reference to FIG. 1 in particular, a printing machine 1 accordingto the invention comprises a section 2 for the supply and preparation ofthe printing ribbon and an adjacent section 3 for the transfer of theimages onto the articles (which are not shown).

The sections 2 and 3 of the machine are advantageously formed so as tobe connectible and disconnectible relative to one another.

The section 2 for the preparation and supply of the printing ribboncomprises a structure 4 in which, in known manner, there are a reel orbobbin 5 for the unwinding of a ribbon R which is inked on one face, andan associated motor-driven reel or bobbin 6 for rewinding the ribbon.

Starting from the unwinding reel 5, the inked ribbon R follows a routeindicated by the arrows F1 and defined by a plurality of guide rollers.

Also provided in the support structure 4 of the section 2 of the machineare an unwinding reel or bobbin 7 for an auxiliary ribbon N or printingribbon, and an associated motor-driven rewinding reel or bobbin 8.

Between the reels 7 and 8, the printing ribbon N follows a routeindicated by the arrows F2.

Downstream of the reels or bobbins 5 and 7, the ribbons R and N travelalong a portion of their respective routes in a juxtaposed condition,both at the same speed which is controlled in known manner.

In particular, the two ribbons R and N pass together between a printinghead 9 and an associated counter-roller 10.

The printing head 9 is, for example, a thermal head of the dot-linetype.

A controlled, selective transfer of thermally meltable ink from theinked ribbon R to the auxiliary ribbon N is brought about between thehead 9 and the counter-roller 10.

Downstream of the printing head 9, the routes of the ribbons R and Nseparate; the used inked ribbon R continues towards the rewinding bobbinor reel 6 and the printing ribbon, with the images formed atpredetermined intervals thereon, continues towards the section 3 of themachine which is intended to perform the transfer of the images onto thearticles.

With reference in particular to FIG. 1, the section 3 of the printingmachine 1 comprises a support framework 11 connected firmly to thesupport structure 4 of the section 2.

The section 3 of the printing machine 1 comprises an upper guide roller12 with a substantially horizontal axis, mounted on a verticallytranslatable slide 12 a for the ribbon N which comes, provided with theimages to be printed, from the section 2 of the machine. Downstream ofthe roller 12 there is a further roller 13.

Downstream of the roller 13 the route of the ribbon N in the section 3of the machine is defined substantially by three pairs of parallel andaligned guide rollers, the pairs being indicated R1, R2 and R3,respectively.

The rollers R1 have their respective axes lying in a common first,substantially horizontal plane and include between them, in front of athermal-transfer device generally indicated 14, a portion of the ribbonN sufficient to contain an image to be printed.

As will become clearer from the following description, the guide rollersR1 are operatively movable vertically away from and towards the articleswhich are to receive the printing.

The rollers R2 of the second pair are arranged upstream and downstreamof the rollers of the first pair R1, respectively, and are also alignedand parallel with one another as well as with the rollers of the firstpair. The rollers R2 lie in a common, substantially horizontal plane.

As will become clearer from the following description, the rollers R2are also operatively movable vertically away from and towards the pathof the articles which are to receive the printing.

The guide rollers R3 are disposed upstream and downstream of the rollersR2 but are fixed vertically.

The arrangement of the rollers R1, R2 and R3 is, in particular, suchthat the portions of the ribbon N included between the rollers R1 andthe rollers R2 and the portions included between the rollers R2 and R3are substantially parallel with one another and hence substantiallyvertical. When the ribbon N has left the guide roller R3 which isdownstream of the thermal-transfer device 14, it returns towards therewinding reel or bobbin 8, following a route defined by furtherdeflecting rollers 15 and 16 of the section 3 of the machine and adeflecting roller 17 of the section 2.

The device 14 for the thermal transfer of the images forms part of amore complex unit, generally indicated 18 in the drawings, which istranslatable relative to the framework 11 of the section 3 of themachine along a horizontal guide indicated 19 in FIGS. 2 and 4. The unit18 is connected, in particular, to a slide 20 which is translatablealong the guide 19 under the action of an electric motor (not shown butof known type).

The unit 18 comprises a fluid cylinder 22, for example, a pneumaticcylinder. The cylinder has a body 22 a the upper end of which is fixedto the slide 20. The rod 22 b of the cylinder projects below the body 22a and is connected firmly to an upper cross-member 23 a of aload-bearing structure, generally indicated 23 (see in particular FIG.2).

The load-bearing structure 23 has a substantially annular shape with arectangular cross-section, with a vertical axis, with two shortervertical side walls 24 and 25 and two longer vertical side walls 26 ofwhich only one is visible in the drawings (FIG. 3).

As can be seen in particular in FIG. 2, the rear side wall 25 of theload-bearing structure 23 has an upper extension which projects upwardsand to which an electric motor 28 with a horizontal axis is fixed bymeans of a connecting plate 27. The shaft of the electric motor 28 iscoupled with a horizontal transmission shaft 29 by means of atransmission comprising a belt 30 stretched between a drive pulley 31keyed to the shaft of the motor 28 and a driven pulley 32 keyed to oneend of the transmission shaft 29.

As can be seen in FIG. 2, the transmission shaft 29 is supported in asubstantially cantilevered manner by means of a ball bearing 33 mountedin a seat provided in the rear side wall 25 of the load-bearingstructure 23. By virtue of this mounting, the transmission shaft 29 canperform limited pivoting movements about the axis of the bearing 33.

The end of the transmission shaft 29 facing the front wall 24 of thestructure 23 is shaped as a tube 29 a (FIG. 2) and carries externally aring gear 29 b which is coupled, by means of a series of gears generallyindicated 34, with an external ring gear 35 a of a heating roller 35which forms part of the thermal-transfer device 14.

The heating roller 35 is mounted in close contact with an underlyingrotatable transfer roller 36 which is intended positively to bring aboutthe transfer onto underlying articles of the images that are carried bythe ribbon N interposed therebetween.

A so-called resistive heating “cartridge” 137 is mounted axially in theheating roller 35 in known manner, for generating the necessary heat.

In operation, activation of the electric motor 28 brings about rotationof the transmission shaft 29 by means of the belt transmission 30-32.The transmission shaft 29 sets the heating roller 35 in rotation bymeans of the gears 29 b, 34 and 35 a and the hot surface of the heatingroller 35 transfers heat onto the active outer surface 36 a of thetransfer roller 36.

The thermal-transfer device with the rollers 35 and 36 is advantageouslysubstantially of the type described in the Applicant's European patentapplication EP-A-0 856 416.

The above-described components of the thermal-transfer device 14 aresupported for rotation by a structure which comprises two end walls orplates 37 and 38 (FIG. 2) and which houses the load-bearing structure23.

In the embodiment shown by way of example, the support structure of thethermal-transfer device 14 is supported by a pair of screws 39 and 40(FIG. 2) which are screwed into the end walls 24 and 25 of theload-bearing structure 23 and the ends of which extend in slot-shapednotches formed in the lower edges of the walls or plates 37 and 38. Afurther screw 41, screwed through the wall 37, has a smooth end whichfits into the tube-shaped end 29 a of the transmission shaft 29.

A plate-like element connected rigidly to the movable rod 22 b of thecylinder 22 is indicated 42 and has an opening 42 a through which thetransmission shaft 29 extends with ample clearance. A Belleville washeror bell spring 43 is fixed to the lower end of the element 42 and bearswith its peripheral portion on a plurality of balls or spheres 44mounted in a recessed seat of a disc 45 fixed to the support structureof the thermal-transfer device 14. A further ball or sphere 46 iscarried centrally in a recess of the disc and its upper portion isnormally spaced from the top portion of the Belleville washer 43.

The above-described arrangement is such that the thermal-transfer device14 can easily be removed from the load-bearing structure 23 for repairor maintenance. For this purpose, it suffices to remove the screws39-41, after which the thermal-transfer device 14 can easily be slid outof the load-bearing structure 23 through the lower end thereof.

The arrangement is also such that the thermal-transfer device 14 canperform limited pivoting movements relative to the load-bearingstructure 23 so that if, during the initial stage of coupling with anunderlying article (with the ribbon N interposed), the contact betweenthe transfer roller 36 and the article does not take place perfectly ona generatrix of the roller, the device 14 as a whole can pivot slightlyand this enables the contact to be improved appreciably.

As can be seen in particular in FIG. 3, each guide roller R1 is carriedby a respective quadrilateral structure, generally indicated 50. Thisstructure comprises an upper cross-member 51 and a lower cross-member 52fixed to the upper ends and to the lower ends, respectively, of twopillars 53 that are mounted for sliding in respective ducts 54 formed inthe load-bearing structure 23 in the vicinity of the lateral verticalcorners thereof.

The pillars 53 have respective radial enlargements 53 a in anintermediate region. Helical springs 55 are arranged around the pillars53 between the respective enlarged portions 53 a and radial stops 54 athat are provided lower down in the associated seats or ducts 54. Thesprings 55 tend to urge the quadrilateral structure 50 upwards relativeto the load-bearing structure 23.

The position of each quadrilateral structure 50 relative to theload-bearing structure 23 can be adjusted manually by means of a screwmember 57 which extends with clearance through an opening in the uppercross-member 51 of the quadrilateral structure and is screwed into athreaded hole provided in the load-bearing structure 23. The screwmember 57 is provided, at its upper end, with a knob-like grip 58 whichfacilitates its rotation.

Respective, very stiff, helical springs 59, in particular stiffer thanthe springs 55, are arranged between the knobs 58 and the associatedcross-members 51 of the quadrilateral structures 50, around the screwmembers 57.

The adjustment of the position of the quadrilateral structures 50relative to the load-bearing structure 23 is in any case such asgenerally to leave a small vertical clearance, for example of 5-6 mm,between the cross-members 51 of the quadrilateral structures and thestructure 23.

Rotation of the knobs 58 and adjustment of the relative positions of thequadrilateral structures 50 in fact adjusts the position of the guiderollers. R1 relative to the transfer roller 36 of the thermal-transferdevice 14 during the stage of the lowering of the roller 36 and of thecontact with an underlying article. At rest, the arrangement is, forexample, that shown in FIG. 1 in which the roller 36 is slightly raised,for example, by a distance of 5-6 mm, relative to the portion of theribbon N which is disposed between the rollers R1.

It is pointed out that the relative position of each quadrilateralstructure 50 is adjustable independently of that of the other. Thisconsequently enables the position of each of the rollers R1 relative tothe transfer roller 36 to be adjusted independently of that of the otherroller R1.

A plate which is fixed beneath the cross-member 51 of each of thequadrilateral structures 50 is indicated 60 in FIGS. 2 and 3. Each plate60 has a respective, substantially horizontal, slot-like opening 61.

With reference now to FIG. 4 in particular, each upper guide roller R2is mounted rotatably in a substantially U-shaped structure 62 arrangedlying down, that is, a horizontally elongated C-shaped structure. Thelower end of a corresponding pair of pillars 63 is connected to theupper horizontal arm 62 a of each of the structures 62; the pillars 63extend slidably in corresponding ducts 64 formed in two walls or plates65 fixed to the framework 11 of the section 3 of the printing machine(see also FIG. 1).

The pillars 63 of each pair are interconnected at the top by a rigidhorizontal structure 66. A plate 67, fixed firmly to this structure(FIG. 4), extends vertically downwards and terminates forming asubstantially horizontal opening or slot 68.

As can be seen in FIG. 4, a lever 70 is mounted at a fulcrum 71 on eachstationary wall or plate 65 so as to be pivotable about a substantiallyhorizontal axis. Each lever 70 has an intermediate transverse pin 72which extends through the slot 68 of a plate 67 and an end pin 73 whichextends through the slot 61 of the plate 60 fixed to one of theabove-described quadrilateral structures 50. The distance of the pin 73from the fulcrum 71 is twice the distance of the pin 72 from thatfulcrum.

The levers 70 enable the magnitudes of the vertical movements of therollers R2 to be linked with those of the rollers R1 on the basis of avery precise relationship, that is, in a ratio of 1:2.

The above-described printing machine operates in the following manner.

In the section 2 of the machine, the ribbons R and N are moved in steps.Upon each step, the printing head 9 transfers an image formed bythermally meltable ink from the inked ribbon R to the ribbon N.

A new image, carried by the ribbon N on its downwardly-facing face, iscorrespondingly presented in front of the transfer roller 36 between theguide rollers R1 upon each step.

The control system of the machine then brings about activation of thecylinder 22 and downward movement of its rod 22 b. The rod urgesdownwards the entire load-bearing structure 23 and the thermal-transferdevice 14 connected thereto.

After a first travel corresponding to the vertical clearance between thecross-members 51 and the structure 23, the downward movement of theload-bearing structure 23 also brings about downward movement of thequadrilateral structures 50 to the bottom of which the guide rollers R1are connected.

The transfer roller 36 is thus brought into contact with the upper faceof the portion of ribbon N included between the rollers R1.

The control system of the machine 1 then brings about a translation ofthe unit generally indicated 18, in a horizontal direction. During thisstage, the transfer roller 36, which is heated as a result of therotational contact with the heating roller 35, performs the thermaltransfer of the image from the ribbon N onto the underlying article. Theperipheral velocity of the roller 36 is advantageously equal to thespeed of translation of the unit 18.

It should be noted that, during the image-transfer stage, the portion ofthe ribbon N that is engaged by the transfer roller 36 is stationarylocally and, in particular, is not subjected to any horizontal movement.This is permitted by the particular arrangement of the guide rollers R1,R2 and R3 and by the transmission with a ratio of 1:2 which links thevertical movements of the rollers R2 and R1.

Upon completion of the thermal transfer of the image, the control systemof the machine causes the support structure 23 to be raised again bymeans of the cylinder 22. During this stage, first of all thethermal-transfer device 14 is raised and then the guide rollers R1 andR2 are raised. The machine thus tends to return to the configurationshown in FIG. 1.

The fact that the vertical positions of each of the rollers R1 can beadjusted independently enables one of them optionally to be keptslightly higher than the other. This may be advantageous, according tothe characteristics of the ribbons N used, to facilitate detachment ofthe ribbon from the article after the transfer of an image.

The control system of the machine can then bring about the return of theunit 18 to the starting position and, at the same time, the execution ofa further step (the formation of a new image). The operation continuesin the manner described above.

FIGS. 5 to 12 show another printing machine according to the presentinvention. In these drawings, parts and elements identical orsubstantially equivalent to parts and elements already described abovehave again been given the same reference numerals or letters.

In the machine according to FIGS. 5-12, the section 2 for thepreparation and supply of the printing ribbon N provided with images issubstantially identical to the section 2 of the machine described abovewith reference to FIGS. 1 to 4.

The machine according to FIG. 5 is thus distinguished substantially withregard to the section 3 for the thermal transfer of the images.

In the machines according to FIG. 5, et seq. the section 3 comprises amovable unit generally indicated 118, connected to a slide 120 mountedso as to be translatable along an upper guide bar 119. As can be seen inparticular in FIG. 6, the guide bar 119 extends transversely.

The movement of the slide 120 and of the associated movable unit 118 isbrought about by means of an electric motor 121 (FIG. 6) and of anassociated belt or chain transmission and respective pulleys, generallyindicated 122.

The thermal-transfer device 14 comprises a heated pad 136 in which aso-called resistive heating cartridge 137 is incorporated in knownmanner.

The pad 136 has an arcuate lower surface or face 136 a the convex sideof which faces downwards (see, for example, FIG. 7).

The pad 136 is fixed to a substantially fork-like body 80 having twoparallel portions or arms 80 a which extend vertically upwards (againsee FIG. 7). The arms 80 a of the body 80 are articulated at 81 to theupper ends of two arms 82 a of a similar fork-shaped body 82 fixed tothe movable portion 22 b of the cylinder 22 (FIG. 5).

The articulation axis 81 of the shaped body 80 extends substantiallyhorizontally and represents the axis of the cylinder on which thearcuate surface 136 a of the thermal-transfer pad 136 theoreticallyextends. The radius of this cylinder is indicated R₀ in FIG. 7.

A linear rack, indicated 83 (FIGS. 5, 7, 8-12) is fixed (in the mannershown in FIG. 5) to the movable portion 22 b of the cylinder 22. Thisrack 83, which has its teeth facing downwards, is also connected (FIGS.7-12) to a vertical sleeve 84, slidable along a guide 85.

The guide 85 is in turn connected to similar guides 86 (FIGS. 8 and 9)by means of an upper cross-member 87 in which a horizontal slot-shapedopening 88 is formed. The guides 85 and 86 are fixed, at the bottom, toa cross-member 89 to which the guide rollers R1 are in turn connected.

As can be seen in FIG. 7, two springs 140 are stretched between anengagement provided in the intermediate portion of the sleeve 84 and acrosspiece 141. This crosspiece 141 bears on two upper extensions 84 aof the sleeve 84. In the condition shown in FIG. 7 (pad 136 raised), thecrosspiece 141 is disposed at a predetermined distance (for example 5-6mm) from the underlying cross-member 87.

A further rack having a convex arcuate shape with the teeth also facingdownwards is indicated 90 (FIGS. 5, 7 and 10-12). The arcuate rack 90 isfixed to the body 80 which carries the heating pad 136, as shown in FIG.5.

As can be seen, for example, in FIG. 7, the straight rack 83 meshes witha sprocket 91 coaxial with a sprocket 92 of smaller diameter.

The sprockets 91 and 92 are carried rotatably by the body 82 which isfixed to the movable portion 22 b of the cylinder 22 (see FIG. 5).

The arcuate rack 90 has a radius indicated r₀ in FIG. 7. The centre ofcurvature of this rack lies on the axis of pivoting 81 of the body 80which carries the heating pad 136.

The sprockets 91 and 92 have respective radii (R′₀ and r′₀) which are inthe same proportion to one another as the radii R₀ and r₀, that is:R₀:r₀=R′₀:r′₀.

In operation, a translation of the slide 120 along the guide 119 causesthe sprockets 91 and 92 to roll on the associated racks 83 and 90. Byvirtue of the above-defined geometrical relationship between the radii,the translation of the slide 120 and of the cylinder 122 fixed firmlythereto leads to pivoting of the body 80 and of the associated heatingpad 136 about the axis 81, as can be seen by a comparison of FIG. 10 andFIG. 11 or FIG. 12. The pivoting of the body 80 and of the pad 136 is,in particular, such that, at every moment, the active end surface 136 aof the pad is tangential to a horizontal plane at a point (or ratheralong a line) which is vertically aligned with the pivoting axis 81.

In other words, the pad 136 pivots about the axis 81 as if the pad werea “sector” of a wheel of radius R₀ having its centre on the axis 81.

The upper guide rollers R2 in the machine of FIG. 5 et seq. are carriedby a horizontal structure 95 (FIGS. 5, 8 and 9) which is connected tothe lower ends of two vertical bars or pillars 96 which are translatablevertically in guided manner and are interconnected at the top by atransverse structure 97.

A lever, indicated 170 in FIGS. 8 and 9, has one end articulated at afulcrum 171 and has, in its intermediate region, a transverse pin 172which extends through a horizontal slot-like opening 168 of thecross-member 97. The lever 170 has, at its free end, a furthertransverse pin 173 which engages in the horizontal slot-like opening 88of the cross-member 87. The distance between this pin 173 and thefulcrum 171 is twice the distance between the pin 172 and the fulcrum.

In operation, a downward movement of the movable portion 22 b of thecylinder 22 brings about lowering of the bodies 82 and 80 and hence ofthe thermal-transfer pad 136. At the same time, corresponding loweringof the straight rack 83 and of the associated vertical sleeve 84 isbrought about. After an initial downward travel of a magnitude equal tothe distance between the crosspiece 141 and the cross-member 87, thefurther downward movement of the sleeve 84 causes the pillars 85 and 86and the associated cross-members 87, 89 to be carried along, bringingabout corresponding lowering of the lower guide rollers R1.

The distal end of the lever 170 thus performs a downward pivotingmovement about the fulcrum 171 and, by means of its intermediate pin172, brings about lowering of the structure formed by the pillars 96 andby the cross-members 97 and 95, as well as of the associated upper guiderollers R2, by a distance which is half that of the lowering of thelower guide rollers R1.

This enables the portion of the ribbon N which is disposed between theguide rollers R1 to be kept substantially stationary in a horizontaldirection.

As soon as the heating pad 136 has performed its downward movement, thecontrol system of the machine brings about translation of the slide 120along the guide 119. This leads to pivoting of the pad 136 about theaxis 81, as described above. The heating pad 136 thus performs a rollingmovement in a transverse direction on the portion of the ribbon N whichis interposed between the pad 136 and an underlying article.

Naturally, the control system of the machine can be arranged to startthis rolling movement from an extreme position such as the position ofFIG. 11 or FIG. 12, or from an intermediate position such as that shownin FIG. 10.

Advantageously, as shown in FIGS. 8 and 9, the fulcrum 171 about whichthe lever 170 is articulated is not constantly stationary relative tothe load-bearing structure 11 of the printing machine but rather iscarried by a body 101 fixed to a rod 102 a of a pneumatic cylinder 102fixed to the structure of the machine. The cylinder 102 is normally keptin the condition shown in FIGS. 8 and 9 by the supply of a suitablefluid pressure to the interior of its body.

Each time the printing of an image on an article is completed, thecontrol system of the machine can advantageously bring about thedischarge of the pressure in the cylinder 102 so that the rod 102 a candescend, bringing the fulcrum 171 of the lever 170 with it, although inopposition to a weak spring 103.

When the control system of the printing machine causes the movableportion 22 b of the main cylinder 22 and the pad 136 connected theretoto be raised, the guide rollers R2 are braked in their upward movementif the ribbon N is adhering to the article. In this case, the rollers R2“brake” the intermediate pin 172, whereas the pin 173 can continue torise. The fulcrum 171, which is no longer blocked by the cylinder 102,is consequently lowered. A pull is thus exerted on the opposite ends ofthe portion of the ribbon N from which the image just printed has beentransferred. The two edge portions of the portion of the ribbon N justused are thus pulled in directions tending gradually ever more towardsthe vertical and this renders the pulling action exerted on this portionof the ribbon more effective and the ribbon can therefore easily bedetached from the article.

Upon completion of the cycle, that is, when the movable portion 22 b ofthe cylinder 22 has returned to the raised, starting position, takingthe rollers R1 with it, the control system reapplies the pressure to thecylinder 102 which returns the fulcrum 171 to the normal position. Thiscauses the rollers R2 to rise, forcing the ribbon N to be detached fromthe article if this has not already occurred.

Naturally, the principle of the invention remaining the same, the formsof embodiment and details of construction may be varied widely withrespect to those described and illustrated purely by way of non-limitingexample, without thereby departing from the scope of the invention asdefined in the appended claims.

Thus, for example, as an alternative to the method described above, theimages may be arranged on the printing ribbon N by one of the variousother known methods, for example, those described in the Applicant'sEuropean patent application EP-A-0 572 999.

1. A machine (1) for printing images on articles, comprising a supportstructure (4, 11) in which there are: a thermal-transfer device (14)having a movable active surface (36 a; 136 a) in a position operativelyfacing the path of the articles; supply and guide means (5-10) suitablefor advancing a flexible ribbon (N) in steps along a predetermined routewhich extends partly between the active surface (36 a; 136 a) of thethermal-transfer device (14) and the path of the articles, the flexibleribbon (N) carrying, at predetermined intervals, on the face which isintended to face the articles, images formed with a thermallytransferable ink, and drive means (22) suitable for bringing about asubstantially vertical movement of the active surface (36 a; 136 a) ofthe thermal-transfer device (14) towards the ribbon (N) and an articleso as to press and heat the ribbon against an article in order to bringabout the transfer of an image carried by the ribbon (N); the machine(1) being characterized in that the supply and guide means comprise: afirst pair of aligned, movable guide rollers (R1) which are disposed onthe route of the ribbon (N), upstream and downstream of thethermal-transfer device (14), respectively, with their respective axeslying substantially in a common, first plane, and which can includebetween them a portion of the ribbon (N) containing an image, in frontof the active surface (36 a; 136 a) of the thermal-transfer device (14),the rollers (R1) being operatively movable away from and towards thepath of the articles along a predetermined axis which is arranged at anangle to the plane that contains the axes of the rollers (R1); a secondpair of movable guide rollers (R2), which are disposed upstream anddownstream of the first pair of rollers (R1), are aligned and parallelwith one another and with the rollers of the first pair (R1) and lie ina common, second plane which is substantially parallel to the firstplane, the second pair of rollers (R2) being operatively movable awayfrom and towards the path of the articles along the predetermined axis;and a third pair of stationary and aligned guide rollers (R3), which aredisposed upstream and downstream of the second pair of rollers (R2) andare parallel with one another and with the rollers of the first andsecond pairs (R2, R2); the arrangement of the pairs of rollers (R1, R2,R3) being such that the portions of the ribbon (N) which are includedbetween the first and second pairs of rollers (R1, R2) and the portionswhich are included between the second and third pairs of rollers (R2,R3) are substantially parallel with one another; there being associatedwith the first and with the second pair of guide rollers (R1, R2)movement means (70; 170) such that a movement of the second pair ofrollers (R2) along the predetermined axis is substantially equal to halfof the corresponding movement of the first pair of rollers (R1).
 2. Amachine according to claim 1 in which the first pair and the second pairof movable guide rollers (R1, R2) are carried, respectively, by a firstmovable support structure and by a second movable support structure (50,62-67; 84-87, 95-97) which are coupled with one another mechanically bymeans of a lever (70; 170) that is pivotable relative to a fulcrum (71;171) in the support structure (4) of the machine (1), the movablesupport structures being connected to points (72; 73; 172, 173) of thelever (70; 170) which are disposed, relative to the fulcrum (71, 171),at distances which are in a ratio of 2:1 relative to one another.
 3. Amachine according to claim 1 in which the thermal-transfer device (14)is mounted removably in a load-bearing structure (23) that is movableunder the action of the drive means (22), the thermal-transfer device(14) comprising a motor-driven heating roller (35) that is rotatable incontact with an adjacent transfer roller (36), the heating roller (35)being rotatable about a stationary resistive heating device (137).
 4. Amachine according to claim 3 in which the heating roller (35) comprisesa central tube arranged so as to be rotatable about the resistiveheating device (137) and supported at its ends by means of bearingdevices, the roller (35) having a ring gear (35 a) suitable for enablingit to be rotated by drive means (28-32) mounted on the movableload-bearing structure (23).
 5. A machine according to claim 4 in whichthe drive means comprise an electric motor (28) coupled to a first endof a transmission shaft (29) which has one end mounted so as to berotatable relative to the movable load-bearing structure (23) and theother end (29 b) coupled to the heating roller (35).
 6. A machineaccording to claim 5 in which the transmission shaft (29) is supportedin the movable load-bearing structure (23) in a cantilevered manner witha capability for pivoting.
 7. A machine according to claim 6 in whichthe unit formed by the heating roller (35) and the associated transferroller (36) is mounted in the movable load-bearing structure (23) withthe capability to perform limited pivoting movements.
 8. A machineaccording to claim 2 in which each roller (R1) of the first pair andeach roller (R2) of the second pair is carried by a respective movablesupport structure (50; 62-67).
 9. A machine according to claim 8 inwhich each movable support structure associated with a guide roller (R1)of the first pair is provided with respective adjustment means (57-59)suitable for permitting independent adjustment of its position relativeto that of the above-mentioned movable load-bearing structure (23). 10.A machine according to claim 1 in which drive means (119-122; 83, 90,91, 92) are associated with the thermal-transfer device (14; 136) forbringing about a rolling movement thereof in a direction transverse thedirection of advance of the printing ribbon (N).
 11. A machine accordingto claim 10 in which the thermal-transfer device (14) comprises a heatedpad (136) mounted for pivoting about an axis (71) that is translatabletransversely relative to the structure (11) of the machine (1), the pad(136) having an active end surface (136 a) which is arcuate and convexand lies substantially on a cylinder the axis of which coincides withthe axis (81) of pivoting of the pad (136), the drive means beingarranged in a manner such that, at every moment during a pivotingmovement of the pad (136), its active surface (136 a) is tangential to ahorizontal plane along a line that is aligned vertically with the axisof pivoting (81).
 12. A machine according to claim 11 in which the drivemeans comprise a linear rack (83) which is movable vertically and isstationary horizontally, and with which is meshed a first sprocket (91)fixed firmly to and coaxial with a second sprocket (92) which mesheswith an arcuate rack (90) that is fixed firmly to the pad (136) and iscentred about the axis of pivoting (81) of the pad (136), thearrangement being such that the ratio between the radius of the firstsprocket (91) and the radius of the second sprocket (92) issubstantially equal to the ratio between the radius of the activesurface (136 a) of the pad (136) and the radius of the arcuate rack(90).
 13. A machine according to claim 2 in which controllable means(102) are provided for permitting a movement of the fulcrum (171) of thelever (170).